Seismic Safety, Risk Reduction and
Performance-Based Design
Aimed at Nuclear Facility Structures
Bozidar Stojadinovic, Associate Professor
Department of Civil and Environmental Engineering
University of California, Berkeley
Outline
What is performance-based design?
How to design structures to reduce risk?
What are the safety-increasing
innovations in structural engineering?
Why should we do this for the new
nuclear cycle in the US?
Performance-Based Design
Design to achieve specified results
rather than to adhere to particular
technologies or prescribed means
(Moehle, EERI Distinguished Lecture, 2005)
Directly address the needs of the owner
or user of the system or structure in
their risk environment
Prescription vs. Performance
A code provision
(ASCE 43-05:
6.2.2(a)):
“Minimum joint
reinforcement shall
consist of X-pairs of
#4 diagonal crossties spaced 12 in. on
center.”
Prescription vs. Performance
What is the performance?




Is such joint safe?
If so, what is the level of safety?
If so, how much does it cost to be so safe?
Would #3 cross-ties spaced 6 in. on center
be better or worse? Safer? Less expensive?
Easier to build?
Performance-Based Design:
Earthquake Engineering View
Prof. Mahin, CEE 227 Lectures
Performance-Based Design:
Deterministic Quantification
Prof. Mahin, CEE 227 Lectures
Performance-Based Design:
Probabilistic Quantification
Prof. Mahin, CEE 227 Lectures
How to Design for Performance?
Prof. Mahin, CEE 227 Lectures
Probabilistic Framework
Performance-based Evaluation Example :
How Safe are our Bridges?
Type 1
Type 11
Framework for Bridge Evaluation
Hazard Model
Select and scale
ground motions
8
Magnitude
7
6
5
4
0.1
1
10
100
1000
Distance (km)
Damage Model
discrete
Engineering Demand Parameter (EDP)
continuous
Engineering Demand Parameter (EDP)
Decision Model
Damage Measure (DM)
Damage Measure (DM)
Intensity Measure (IM)
Demand Model
discrete
continuous
Decision Variable (DV)
Framework for Bridge Evaluation
Hazard Model
Do non-linear
time-history
analyses
C
L
Damage Model
discrete
Engineering Demand Parameter (EDP)
continuous
Engineering Demand Parameter (EDP)
Decision Model
Damage Measure (DM)
Damage Measure (DM)
Intensity Measure (IM)
Demand Model
discrete
continuous
Decision Variable (DV)
Framework for Bridge Evaluation
Performance
(damage)
states
Hazard Model
Damage Model
discrete
Engineering Demand Parameter (EDP)
continuous
Engineering Demand Parameter (EDP)
Decision Model
Damage Measure (DM)
Damage Measure (DM)
Intensity Measure (IM)
Demand Model
discrete
continuous
Decision Variable (DV)
Framework for Bridge Evaluation
Hazard Model
Deaths?
Dollars?
Down-time?
Damage Model
discrete
Engineering Demand Parameter (EDP)
continuous
Engineering Demand Parameter (EDP)
Decision Model
Damage Measure (DM)
Damage Measure (DM)
Intensity Measure (IM)
Demand Model
discrete
continuous
Decision Variable (DV)
Framework for Bridge Evaluation
Outcome: Repair
cost ratio
fragility
curves
Demand Model
Sa(T1)=1g
Common Probabilistic Basis for
Civil and Nuclear Structures
Given a seismic hazard environment and a
structure, the probability that a performance
objective is achieved is:
PPO 
 P( PO | hazard) d (hazard)
hazard
Consider probability distributions of seismic
hazard, of demand and of capacity due to:


Lack of knowledge (epistemic uncertainty)
Record-to-record ground motion randomness
(aleatory uncertainty)
Seismic Hazard and
Probability of Failure
Hazard: probability of exceeding a value of
ground motion intensity (hazard curve)
PH  H (s )  k0 (s )
PH
a
PH
a
k
Failure: a comparison demand and capacity
PF  P(C  D )   P ( F sa ) dH ( sa )
sa
DOE-1020 and ASCE 43-05:
(Nuclear) Acceptance Criteria
Probability of failure
is smaller than
probability of hazard
Risk reduction ratio
at the structure level
Performance Category
PH
RR 
PF
Risk Reduction Ratio
PC-1 (conventional)
RR=1.0
PC-2 (internal exposure risk)
RR=1.0
PC-3 (labs, fuel cycle facilities)
RR=10.0
PC-4 (experimental reactors)
RR=20.0
Conventional Design:
Acceptance Criteria


Probability of failure
is, implicitly,
assumed equal to
the probability of
hazard
Design equation:


Capacity reduction
Demand
amplification
at the structural
element level
PF  PH
C  D
Common
Risk-Informed Design Framework
Hazard vs. Failure
Conventional Structures
Nuclear Facility Structures
PH  PF
PH  PF
C
RR
b
k
  D
Design Equation
Common
Risk-Informed Design Framework
New nuclear power plants can be designed
using a risk-informed performance-based
framework
Models for most elements of the structure
exist, including aleatory and epistemic
uncertainties
Modeling can be extended to:
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Other extreme hazards (natural and man-made)
Ageing effects (construction and maintenance)
Accidents (effects on the environment and society)
Risk-based evaluation is used for some
aspects of the nuclear fuel cycle design today
Innovations in Civil Engineering
(DOE NP2010 Initiative)
Over the past 30 years civil engineering
did not stand still:


Technologies ready for deployment
New and promising technologies worthy of
additional exploration and development
Note: this is just the CE side!

No NE-CE-ME synergies were explored
Ready-to-Use CE Technologies
Response modification
devices
Steel-plate sandwich
structures
Advanced concrete
admixtures
Composite plastics for
reinforcement
Pipe bends vs. welded
elbows
Precision blasting for
rock removal
High-deposition rate
and robotic welding
Cable splicing
4-D modeling and BIM
GPS use in construction
Open-top installation
Upcoming CE Technologies
Prefabrication,
preassembly and
modularization
Advanced
information
management and
control during
design and
construction
Earthquake Engineering of
Heavy Structures
Large weight, often
positioned high
above the
foundation
Combat inertia
forces through:

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
Strength
Flexibility
Damping
35m(115ft)
Reactor Cavity
Cooling System
Refueling
Floor
Control Rod Drive
Stand Pipes
Generator
Reactor Pressure
Vessel
Cross Vessel
(Contains Hot &
Cold Duct)
46m(151ft)
Power Conversion
System Vessel
Shutdown Cooling
System Piping
Floors
Typical
32m(105ft)
Steel-plate Sandwich Walls
Steel plate used as:

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Form
Reinforcement
Steel-plate Sandwich Walls
Steel plate used as:


Form
Reinforcement
Composite action
with concrete
enabled using studs
Steel-plate
Sandwich Walls
Steel plate used as:


Form
Reinforcement
Composite action
with concrete
enabled using studs
Limited damage
Steel-plate
Sandwich Walls
Steel plate used as:


Form
Reinforcement
Composite action
with concrete
enabled using studs
Limited damage
Steel-plate
Sandwich Walls
Steel plate used as:


Form
Reinforcement
Composite action
with concrete
enabled using studs
Very strong
Very ductilie, too!
Steel-plate Sandwich Walls
Steel plate used as:


Form
Reinforcement
Modular,
prefabricated
components
Rapid construction
Response Modification Devices
Devices designed to
alter dynamic
response of
structures:


Base isolation, to
reduce input
motion/energy
Added damping, to
dissipate energy that
enters the structure
Base Isolation Concept
Provide a soft,
deformable layer
between the
structure and the
ground
Not new!

Sanjusangendo
Temple in Kyoto,
built in 1164
Base Isolation Concept
Base Isolation Benefits
Reduced motion of
the structure
Reduced
acceleration of the
content
Base Isolation Benefits
Reduced motion of
the structure
Reduced
acceleration of the
content
Problems:

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
Vertical acceleration
Seismic gap
Crossing the gap
Base Isolation Benefits
Reduced motion of
the structure
Reduced
acceleration of the
content
Problems:



Vertical acceleration
Seismic gap
Crossing the gap
Base Isolation Devices:
Laminated Rubber Bearings
Technology
developed in 1980’s
Used in non-nuclear
but safety-critical
structures:

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LNG tanks
Hospitals
Emergency
command centers
Base Isolation Devices:
Friction-Pendulum Bearings
Technology
developed in 1990’s
Used in conventional
building structures
Used in critical
infrastructure:


Bay Area long-span
bridge crossings
Off-shore platforms
Response Modification Devices:
Seismic Dampers
Steel damper
Oil damper
Lead damper
Friction damper
Why Design Based on
Performance?
Integrate the entire nuclear fuel cycle
design to enable transparent riskinformed decisions on:

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Safety
Security
Economy
Effects on the environment (sustainability)
Safety, Security, Economy and
Sustainability
Use simulation to evaluate effects of hazards:

Anticipate before we build them
Balance safety and economy:

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Do what is necessary, no more, no less
Find the sweet spots where small investments
result in significant benefits
Integrate security and sustainability:
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Design right from the get-go
Reduce carbon emissions during construction, too!
Be modular, reuse and recycle
How Do We Get There?
A unique opportunity is here:
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A new building cycle is starting
There is little institutional memory left:
 Bad: there is no experience
 Good: there is no experience!
Form cross-disciplinary engineering teams as
early as possible:


State performance objectives, not prescriptions
Work together to formulate the design process
and execute it right!
Role of Civil/Structural
Engineering
Performance-based design:
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Utilize advances in conventional design to energize
new nuclear construction
Bridge the engineering skill gap in structural and
earthquake engineering
New and emerging technologies:
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Response modification devices
New composite structural systems
Modular construction and maintenance
Modern construction and life cycle management
Thank you!
Bozidar Stojadinovic, Associate Professor
721 Davis Hall #1710
Department of Civil and Env. Engineering
University of California, Berkeley
Berkeley, CA 94720-1710
boza@ce.berkeley.edu
http://www.ce.berkeley.edu/~boza